JPH11281437A - Pulsation absorbing structure for flow meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a good pulsation absorbing structure for a flow meter, which is capable of facilitating accurately flow rate measuring at low costs by reducing the influence of pulsation in the flow meter of an estimation type. SOLUTION: An ultrasonic flow meter 1 is provided with a case main body 2 having an inlet 3 and an outlet 4, a flow rate measuring section 5 for intermittently measuring a physical quantity changed according to the flow velocity of fluids flowing in a measuring duct 5a arranged in the case main body 2, an in-case conduit outlet 6 for communicating the inlet 3 with the upstream side end 5b of the measuring duct 5a, and an in-case outlet conduit 7 for communicating the downstream side end 5e of the measuring duct 5a with the outlet 4, and a ball-like buffer chambers 8a and 8b provided in the midways of the in-case inlet conduit 6 and the incase outlet conduit 7 for dispersing the flowing of fluids.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulsation absorbing structure of a flow meter used as an electronic gas meter or the like.
The flow rate of a guess-type equation that intermittently measures the flow velocity of the fluid in the flow path and estimates the passing flow rate of the fluid that has passed through the flow path by multiplying the measured flow velocity by the cross-sectional area of the flow path and the intermittent time. The present invention relates to a pulsation absorbing structure for reducing the influence of pulsation (pressure fluctuation, flow velocity fluctuation) on a meter.

[0002]

2. Description of the Related Art In recent years, a flow meter used in an electronic gas meter or the like includes a measuring means for intermittently measuring a physical quantity which changes according to a flow velocity of a fluid in a flow path, and a flow rate measured by the measuring means. There is known an inferential flow meter that includes a flow rate measuring unit that measures a passing flow rate of a fluid that has passed through the flow path by multiplying the flow area by multiplying the cross-sectional area of the flow path by the intermittent time. In addition, such a speculative flow meter uses an ultrasonic flow meter that uses an acoustic transducer or the like, which is an element that transmits and receives ultrasonic waves in a fluid, as a measuring means, and a pressure fluctuation of a fluid in a flow path. There is a fluidic type flow meter that uses a fluidic element for detecting the flow rate.

FIG. 4 shows the basic structure of an ultrasonic flowmeter 20 used as an electronic gas meter.
The ultrasonic flowmeter 20 includes a case main body 24 that forms a gas flow path that communicates the inflow port 26 and the outflow port 27, and a flow measurement unit 28 that is a measuring unit disposed in the case main body 24. Have. The flow rate measuring unit 28 includes an upstream chamber 20 a and a downstream chamber 2 in the case main body 24.
0b, and a straight tube-shaped measurement duct 22 which also functions as a gas flow measurement flow path and an ultrasonic wave propagation channel, and a pair of opposedly disposed opposite ends of the measurement duct 22 at a predetermined distance. Sound transducers 21 and 23 are provided. The acoustic transducers 21, 23 comprise, for example, piezoelectric vibrators operating at ultrasonic frequencies.

[0004] The gas flowing into the upstream chamber 20a from the inlet 26 of the case body 24 reaches the downstream chamber 20b through the measuring duct 22, and the outlet 2
Outflow from 7. Therefore, an ultrasonic signal is generated from the acoustic transducer 21 on the upstream chamber 20a side and received by the acoustic transducer 23 on the downstream chamber 20b side, and the propagation time of the ultrasonic signal in the gas flow direction between the acoustic transducers 21 and 23 is determined. to measure the t _1.

Next, both acoustic transducers 21,
By switching the 23, to generate an ultrasonic signal from the downstream chamber 20b side of the acoustic transducer 23, the upstream chamber 20a side gas flow direction by receiving the acoustic transducer 21 of measuring the propagation time t ₂ in the reverse direction . The flow velocity V of the gas flowing in the measurement duct 22 is intermittently obtained based on the difference between the two measured propagation times t ₁ and t ₂ , and the flow velocity V is multiplied by the cross-sectional area of the measurement duct 22. To find the instantaneous flow rate. Further, the instantaneous flow rate is multiplied by a sampling time, which is a constant measurement interval, to obtain a passing flow rate, and the passing flow rates are integrated to obtain an integrated flow rate.
An electronic gas meter can be configured by displaying the integrated flow rate obtained by the flow rate measuring means (not shown) on a display means (not shown) provided on the outer surface of the case main body 24.

[0006]

Among combustors that consume gas supplied through an electronic gas meter, some gas burners, such as gas governors and gas heat pumps (GHPs), apply pressure fluctuations and flow velocity fluctuations to supply gas during use. Some cause pulsation. Then, as shown in, for example, FIG.
When the pulsation 25 propagates from the downstream side of the ultrasonic flowmeter 20 into the flowmeter, the gas flow in the measurement duct 22 may be a pulsating flow.

Further, in the case of LPG collective supply or city gas supply as shown in FIG. 5 (b), a plurality of flow meters 20A and 20B are branched and connected to the main supply pipe 31, so that the upstream flow rate is controlled. The pulsation 25A generated by the combustor 30A connected to the meter 20A may be transmitted to the downstream flow meter 20B through the gas flow in the flow meter 20A and the branch supply pipe 31a. In addition, for example, in the downstream flow meter 20B,
Pulsation 25B from combustor 30B connected to self
And a combustor 30A connected to an upstream flow meter 20A.
And the pulsation 25A from the
A pulsating flow in the flow meter 20B may be further intensified due to the influences of A and 25B. If such a pulsating flow becomes violent and the fluctuation period of the pulsation at the inlet of the flow meter and the fluctuation period of the pulsation at the outlet greatly deviate, backflow may occur in the flow meter in some cases.

In such a flow meter of the guessing type, when a pulsating flow occurs in the gas flow in the measuring duct 22 due to the pulsation generated by the combustor, good measurement cannot be performed in the flow measuring unit 28. In particular, when a backflow occurs in the measurement duct 22, the calculation of the integrated flow rate of the flowmeter is adversely affected. That is, when a pulsating flow occurs in the gas flow in the measurement duct 22, the flow velocity V of the gas flow is measured at a constant sampling interval Δt as shown in FIG. 6, and the measured flow velocity V is multiplied by the sampling time Δt. When the passing flow rate is obtained, the hatched portion in the figure becomes an error, and the integrated flow rate obtained by integrating the passing flow rates is an integrated value that is considerably different from the actual gas usage.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, and a good flow meter capable of reducing the influence of pulsation in a guess-type flow meter and realizing accurate flow measurement easily and at low cost. Is to provide a pulsation absorbing structure.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a case body having an inlet and an outlet, and a physical quantity which is arranged in the case body and changes according to the flow rate of the fluid in the flow path. Measuring means for measuring intermittently, an introduction path in the case communicating the inflow port and the upstream end of the measurement means, and an outflow path in the case communicating the downstream end of the measurement means and the outflow port. A pulsation absorbing structure for a flow meter, wherein at least one of the introduction path in the case and the extraction path in the case is provided with a spherical buffer chamber for diffusing a fluid flow. This is achieved by the pulsation absorbing structure of the flow meter.

According to the above configuration, the pulsating flow entering the case main body from the upstream side or the downstream side of the flow meter causes pressure waves due to the pulsation to spread throughout the chamber due to the diffusion of the fluid flowing into the spherical buffer chamber. The pressure wave propagated uniformly and propagated in the room is absorbed by being uniformly reflected on the entire spherical indoor wall, so that the pulsation transmitted to the measuring means can be reduced. Further, since the spherical buffer chamber itself does not require a movable part or the like and has a very simple structure, the spherical buffer chamber can be easily incorporated into the case body without specially devising the structure and arrangement of the measuring means. .

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pulsation absorbing structure of a flow meter according to an embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic sectional view of an ultrasonic flowmeter 1 provided with a pulsation absorbing structure according to a first embodiment of the present invention.

The ultrasonic flow meter 1 shown in FIG. 1 is used as an electronic gas meter, and includes a substantially rectangular parallelepiped case body 2 having an inlet 3 and an outlet 4, and an inside of the case body 2. A flow rate measuring unit 5 which is a measuring means for intermittently measuring a physical quantity which varies according to a flow velocity of a fluid flowing in the arranged straight tubular measuring duct 5a, and an upstream of the inflow port 3 and the measuring duct 5a A case introduction path 6 communicating with the side end 5d, a case introduction path 7 communicating the downstream end 5e of the measurement duct 5a with the outflow port 4, a case introduction path 6 and the case introduction path. Spherical buffer chambers 8a and 8b are provided in the middle of the lead-out path 7 to diffuse the flow of the fluid.

The flow rate measuring section 5 is a straight tubular measuring duct 5 which also serves as a gas flow rate measuring flow path and an ultrasonic wave propagation pipe.
a, and a pair of acoustic transducers 5b, 5 that are opposed to both ends of the measurement duct 5a at a predetermined distance from each other.
c. A shutoff valve 9 capable of shutting off the inflow of gas is provided in the case introduction path 6 at a position near the inflow port 3. The buffer chamber 8 a on the case introduction path 6 is connected to the shutoff valve 9 and the flow rate. It is provided between the upstream end 5 d of the measuring section 5.

The diameter of the buffer chamber 8a is set to be at least twice the inner diameter of the outlet of the shut-off valve 9 in order to obtain a sufficient buffer effect. In addition, the communication path 10a for communicating the buffer chamber 8a with the flow rate measuring unit 5 can easily provide a pressure wave transmitted from the inflow port 3 into the buffer chamber 8 without being subjected to a buffering action due to diffusion and reflection in the room. It is provided at a position not facing the outlet of the shut-off valve 9 so that it does not come out to the flow measuring unit 5 side, and its inner diameter is set to a small diameter that is appropriately narrowed down from the inner diameter of the outlet of the shut-off valve 9.

On the other hand, the buffer chamber 8 on the outlet path 7 in the case
b, the indoor diameter is set to be at least twice the inner diameter of the outlet of the outlet 4, and the communication path 10 b for communicating the buffer chamber 8 b with the flow rate measuring unit 5 is propagated from the outlet 4 into the buffer chamber 8 b. The pressure wave is provided at a position not opposed to the outlet 4 so that the pressure wave does not easily come out to the flow measuring unit 5 side without being subjected to a buffering action due to diffusion and reflection in the room. 4 is set to a small diameter that is appropriately narrowed from the inner diameter of the outlet.

That is, in each of the buffer chambers 8a and 8b, when the pulsation is propagated, the pressure wave due to the pulsation is evenly propagated throughout the room due to the diffusion of the fluid flowing into the room, and the pressure wave propagated in the room. Is reflected by the spherical interior wall. Therefore, for example, there are no corners or ridges where the reflection performance is deviated compared to the case where the buffer chamber shape is set to a rectangular parallelepiped, etc. An excellent buffer effect can be obtained.

For example, the inlet 3 of the ultrasonic flowmeter 1 is connected to a main gas supply pipe 31 through a branch supply pipe 32.
The main supply pipe 31 is connected to an inlet 13a of another flow meter 13 so as to be located upstream of the ultrasonic flow meter 1. As shown in FIG. 1, a combustor 14A, 14B such as a gas heat pump (GHP) for burning and consuming gas is provided in the outlet 4 of the ultrasonic flow meter 1 and the outlet 13b of the flow meter 13, as shown in FIG. Is connected.

Therefore, in the ultrasonic flowmeter 1 provided with the buffer chambers 8a and 8b in both the case introduction path 6 and the case discharge path 7, the buffer chamber 8 provided in the case introduction path 6 is provided.
a attenuates and reduces the pulsation 15 a transmitted through the branch supply pipe 32 via the upstream flow meter 13 and the like, and reduces the discharge path 7 in the case.
The pulsation 15b transmitted from the combustor 14B to the outlet 4 can be attenuated and reduced by the buffer chamber 8b provided in the above.
Therefore, the flow rate measuring unit 5 is reduced in the influence of the pulsation from both the upstream side and the downstream side, and can realize more accurate flow rate measurement.

The buffer chambers 8a and 8b as the pulsation absorbing mechanism for reducing the propagation of pulsation do not require a movable part or the like and have a very simple structure. It can be easily incorporated into the case main body 2 without special measures, and accurate flow rate measurement can be easily and inexpensively realized.

In the first embodiment, spherical buffer chambers 8a and 8b are provided in both the introduction path 6 and the discharge path 7 in the case.
However, due to space limitations in the case body 2, etc., the buffer chamber 8 is provided in both the case introduction path 6 and the case discharge path 7.
If it is difficult to equip the other flowmeters 13 and 8b with at least one of the upstream flowmeters 13 and the combustors 14A and 14B, a sufficient pulsation absorbing mechanism is provided. Since only the pulsation transmitted from either the upstream side or the downstream side of the total 1 needs to be considered, the spherical buffer chamber 8 is provided only in one of the introduction path 6 and the discharge path 7 in the case. What is necessary is just to make it the structure which did.

FIG. 2 shows an ultrasonic flowmeter 1A according to a second embodiment of the present invention in which a spherical buffer chamber 8 is provided only in the discharge passage 7 in the case, and FIG. 3 shows an ultrasonic flowmeter 1B according to a third embodiment of the present invention equipped with the buffer chamber 8 described above. These flow meters 1A, 1B
Since the configuration other than the buffer chamber 8 is exactly the same as that of the ultrasonic flowmeter 1 of the first embodiment, the same reference numerals are given and the detailed description is omitted.

As shown in FIG. 2, when the spherical buffer chamber 8 is provided only in the discharge passage 7 in the case, the case body 2 is connected to the combustor 14 connected to the outlet 4 of the flow meter 1A.
The pulsation 15b propagated into the inside is efficiently absorbed by the buffer chamber 8, and the influence on the flow rate measuring unit 5 can be reduced.

As shown in FIG. 3, a spherical buffer chamber 8 is provided.
Is installed only in the introduction path 6 in the case, the flow meter 1
The pulsation 15a propagated into the inlet 3 from another flow meter 13 or the like branched and connected upstream of the branch supply pipe 32 connected to the inlet 3 of B is efficiently absorbed by the buffer chamber 8. In addition, the influence on the flow measurement unit 5 can be reduced.

Further, the configurations of the case body, the measuring means and the buffer chamber in the present invention are not limited to the configurations of the above-described embodiments, but it is needless to say that they can be appropriately changed based on the gist of the present invention. . For example, in each of the embodiments described above, the pulsation absorbing structure of the ultrasonic flow meter has been described. However, the pulsation absorbing structure of the flow meter of the present invention is not limited to this. Can be applied to the inferential flow meter of
The present invention is not limited to P gas and city gas, and can be applied to fluids other than gas, such as water and oil.

[0026]

As described above, according to the pulsation absorbing structure of the flow meter according to the present invention, the pulsating flow entering the case body from the upstream side or the downstream side of the flow meter flows into the spherical buffer chamber. With the diffusion of the fluid, the pressure wave due to the pulsation is evenly propagated throughout the room, and the pressure wave propagated inside the room is absorbed by being uniformly reflected on the entire spherical indoor wall, so that it is absorbed by the measuring means. The transmitted pulsation can be reduced.

Further, since the spherical buffer chamber itself does not require a movable part or the like and has a very simple structure, it can be easily incorporated into the case body without specially devising the structure and arrangement of the measuring means. be able to. Therefore, it is possible to provide a good pulsation absorbing structure of a flow meter which can reduce the influence of pulsation in a guess-type flow meter and realize accurate flow measurement easily and at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an ultrasonic flowmeter provided with a pulsation absorbing structure according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view of an ultrasonic flowmeter provided with a pulsation absorbing structure according to the first embodiment of the present invention.

FIG. 3 is a schematic sectional view of an ultrasonic flowmeter provided with a pulsation absorbing structure according to the first embodiment of the present invention.

FIG. 4 is a schematic sectional view showing a basic structure of an ultrasonic flowmeter.

FIG. 5 is a configuration diagram illustrating generation and influence of pulsation.

FIG. 6 is an explanatory diagram of a measurement error caused by pulsation when calculating a flow rate from a measured value of a flow velocity.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic flow meter 2 Case main body 3 Inflow port 4 Outflow port 5 Flow measurement section 5a Measurement duct 6 Introductory path in case 7 Outlet path in case 8a Buffer chamber 8b Buffer chamber 9 Shut-off valve 10a Communication path 10b Communication path

Claims (1)

[Claims] 1. A case body having an inflow port and an outflow port, and measurement means disposed in the case body and intermittently measuring a physical quantity that changes according to a flow rate of a fluid in a flow path;
A pulsation absorbing structure of a flow meter including an in-case introduction path that communicates the inflow port with the upstream end of the measurement means, and an in-case induction path that communicates the downstream end of the measurement means with the outflow port. A pulsation absorbing structure for a flow meter, wherein a spherical buffer chamber for diffusing a fluid flow is provided in at least one of the introduction path in the case and the extraction path in the case.